A known dimension measurement device includes a rectangular parallelepiped storage receptacle for storing a measurement object such as a parcel to drop off, an imager fixed at a vertex of the upper surface of the storage receptacle, and an image processor for performing image processing on an image, captured by the imager, of the measurement object (see, for example, Patent Literature 1).
However, any distortion in the image captured by imager would make it difficult for the dimension measurement device disclosed in Patent Literature 1 to accurately measure the size of the measurement object.